A majority of refining, petrochemical and chemical industrial processes rely upon upstream adsorptive, single or multiple guard beds to adsorb low levels of process contaminants (e.g., catalyst poisons) to protect the catalysts in a downstream reactor.
Japanese Patent Pub. 4198139 discloses a process for producing an alkylbenzene compound by alkylating benzene using a solid acid catalyst, preferably an aluminosilicate, especially zeolite. In order to suppress reduction in activity of the solid acid catalyst caused by basic compounds (e.g., catalyst poisons), benzene is treated to remove basic compounds by contacting the benzene with clay, especially activated clay prepared by acidifying bentonite, or by contacting the benzene with a zeolite, active carbon, silica gel, or alumina.
U.S. Pat. No. 5,109,139 discloses a process for purifying a hydrocarbon feedstock which contains linear paraffins and at least one impurity (e.g., catalyst poisons) selected from the group consisting of aromatic compounds, nitrogen-containing compounds, sulfur-containing compounds, oxygen-containing compounds, color bodies, and mixtures thereof, said process comprising the steps of: a) contacting a liquid feed stream comprising said hydrocarbon feedstock with an adsorbent containing desorbent in an adsorbent bed under conditions comprising temperature and space velocity and for a cycle time suitable for the adsorption of said at least one impurity by said adsorbent to result in an adsorbent cycle effluent comprising purified hydrocarbon feedstock and an amount of said desorbent; b) monitoring said amount of desorbent in said adsorbent cycle effluent to determine a desorbent plateau level which corresponds to a level of said at least one impurity in said feed stream; and c) continuing said monitoring of step b) until said amount of desorbent is detected as dropping below said desorbent plateau level thereby indicating that breakthrough of said at least one impurity is occurring in said adsorbent cycle effluent and that said adsorbent is substantially saturated with said at least one impurity to result in an impurity-loaded adsorbent.
International Pub. WO9807673 discloses a process for preparing an alkylated benzene or mixture of alkylated benzenes which involves contacting a benzene feedstock with a solid acid, such as an acidic clay or acid zeolite, in a pretreatment zone at a temperature greater than about 130° C. but less than about 300° C. to form a pretreated benzene feedstock, and thereafter contacting the pretreated benzene feedstock with (a) alkylating agent in an alkylation zone, or (b) a transalkylating agent in a transalkylation zone, in the presence of an alkylation/transalkylation catalyst so as to prepare the alkylated benzene or mixture of alkylated benzenes. The benzene feedstock may contain impurities (e.g., catalyst poisons), such as oxygen, oxygenates, and nitrogen-containing organic compounds. The pretreatment step improves the lifetime of the alkylation/transalkylation catalyst by removing such impurities from the benzene feedstock.
U.S. Pat. No. 6,313,362 discloses a process in which an alkylation product is contacted with a purification medium in a liquid phase pre-reaction step to remove impurities (e.g., catalyst poisons) and form a purified stream. The purified stream may then be further processed by liquid phase transalkylation to convert the polyaklated aromatic compound to a monoalkylated aromatic compound. The process may use a molecular sieve catalyst such as MCM-22 as the purification medium in the pre-reaction step because of its high reactivity for alkylation, strong retention of catalyst poisons and low reactivity for oligomerization under the pre-reactor conditions. Impurities such as olefins, diolefins, styrene, oxygenated organic compounds, sulfur containing compounds, nitrogen containing compounds, and oligomeric compounds are removed.
U.S. Patent Pub. 2008/0139857 discloses processes suitable for purifying aromatic-containing feed streams, and processes using such purified streams are described, wherein the purification processes comprise: (a) providing a process feed stream comprising an aromatic component and impurities (e.g., catalyst poisons); and (b) bringing the process feed stream into contact with a first zeolite and a second zeolite, wherein the first zeolite has a mean pore size of 0.3 to 0.5 nm, and the second zeolite has a mean pore size of 0.6 to 0.8 nm.
Further, it is disclosed that the catalysts used in alkylation reactions in particular bind impurities very strongly and quickly become exhausted as a result of poisoning when the starting materials are not purified adequately. In the alkylation reaction, which is usually operated continuously, the catalyst is, for example, arranged as a fixed bed. In the case of a fresh catalyst, the reactive zone, i.e., the region within which the exothermic reaction (e.g., of benzene with ethylene to form ethylbenzene) occurs, is at the beginning of the fixed bed, viewed in the flow direction. As the period of operation increases, the reactive “hot” zone travels further along in the flow direction, since the beginning of the catalyst bed becomes increasingly laden with the impurities and thus deactivated, i.e., is no longer catalytically effective. When the reactive zone finally arrives at the end (outlet) of the fixed bed, the total amount of catalyst has become deactivated.
It is disclosed that this effect can, for example, be measured by means of temperature measurements in the fixed catalyst bed: temperature measurement points located in succession along the fixed bed in the flow direction show the profile of the exothermic reaction over the fixed bed. If the temperature at the beginning of the fixed bed rises sharply, based on the temperature of the feed stream, a significant part of the conversion occurs here. If the temperature increase at the beginning of the fixed bed is small but that further downstream is high, the reaction has moved downstream. (If the temperature does not also increase at the end of the fixed bed, the catalyst bed is exhausted over its entire length and has to be replaced or regenerated.)
European Patent Pub. 2110368 discloses a process for the alkylation of an aromatic substrate (e.g., alkylation of benzene with ethylene), and a process for the transalkylation of polyalkylated aromatic components (e.g., transalkylation of diethylbenzene with benzene), wherein the nitrogen-containing impurities in the aromatic substrate feedstock and/or the alkylating agent feedstock are monitored in a range 15 wppb to 35 wppm by dry colorimetry.
U.S. Patent Pub. 2009/0326291 discloses a method for treating a hydrogenation feed stream comprising one or more aromatic compounds (e.g., benzene), one or more nitrogen compounds (e.g., catalyst poisons), and one or more unsaturated aliphatic hydrocarbons (e.g., C4-C6 diolefins), the method comprising contacting the hydrogenation feed stream with a hydrogenation catalyst to selectively hydrogenate the unsaturated aliphatic hydrocarbons. In some embodiments, the hydrogenated effluent is contacted with a zeolitic guard bed to remove at least a portion of the one or more nitrogen compounds.
While these references provide methods for monitoring process catalysts or removing catalyst poisons from aromatic feed streams used in catalytic processes, these references, do not provide a method to predict the time in which a guard bed material used to remove a catalyst poison from feed streams should be removed for replacement and/or regeneration. Such guard bed materials, located upstream of and in fluid communication with downstream process catalysts, protect such process catalysts and slowly deactivate due to the accumulation of catalyst poisons. When the catalyst poison capacity of the guard bed material is reached or exceeded, the catalyst poisons then break through the guard bed and contaminate the downstream process catalyst, causing sudden deactivation of such catalysts. This sudden catalyst deactivation can result in significant loss of production, necessitating an unscheduled shut down of the entire process unit for change-out of the process catalysts.
Therefore, there is a need for a method to monitor the real time performance of the guard bed material. Also, there is a need to predict the time in which such guard bed material should be removed for replacement and/or regeneration prior to catalyst poison break through, thereby enabling reliable and seamless production using the process catalyst. This disclosure meets this and other needs.